Packet-switched Ethernet networks (LAN=Local Area Network) are employed both in the industrial and the office environment, where the demands placed on networks are very different. In contrast to the office environment, LANs in day-to-day industrial applications must operate reliably under extreme conditions, such as electromagnetic noise fields, high operating temperatures and mechanical stresses. As the failure of a production plant and the downtimes associated therewith are as a rule bound up with high costs, it is also the case that in industrial applications, failsafe requirements are more exacting than in the office environment.
For this reason, industrial LANs generally employ robust components that enable high-speed redundancy mechanisms, thereby minimizing costs in the event of a fault. In addition a ring topology is usually selected for the network, as this enables a rapid reconfiguration time of less than 500 ms in the case of the failure of a data link or a bridge. Ethernet standard-based standard or proprietary network protocols are generally employed as network protocols for industrial LANs.
By contrast, LANs in office environments are mostly of star-shaped or mesh-type topology and nowadays as a rule employ RSTP (RSTP=Rapid Spanning Tree Protocol) according to IEEE Standard 802.1w as their protocol.